Variable: fill-separate-heterogeneous-words-with-space
fill-separate-heterogeneous-words-with-space is a customizable
variable defined in fill.el.gz.
Value
nil
Documentation
Non-nil means to use a space to separate words of a different kind.
For example, when an English word at the end of a line and a CJK word
at the beginning of the next line are joined into a single line, they
will be separated by a space if this variable is non-nil.
Whether to use a space to separate such words also depends on the entry
in fill-nospace-between-words-table for the characters before and
after the newline.
This variable was added, or its default value changed, in Emacs 26.1.
Source Code
;; Defined in /usr/src/emacs/lisp/textmodes/fill.el.gz
(defcustom fill-separate-heterogeneous-words-with-space nil
"Non-nil means to use a space to separate words of a different kind.
For example, when an English word at the end of a line and a CJK word
at the beginning of the next line are joined into a single line, they
will be separated by a space if this variable is non-nil.
Whether to use a space to separate such words also depends on the entry
in `fill-nospace-between-words-table' for the characters before and
after the newline."
:type 'boolean
:version "26.1")